Neuropathic pain is a chronic pain state caused by injury of the nervous system and there are various conditions associated with it such as diabetic neuropathy, postherpetic neuralgia, cancer pain, trigeminal neuralgia, cervical radiculopathy and anticancer and anti-HIV-induced neuropathic pain. The pathophysiological role of voltage-gated T-type calcium channels in neuropathic pain has been well documented. ABT-639 is a peripherally acting, selective T-type calcium channel blocker and it is shown to efficiently reduce nociceptive and neuropathic pain in rats in multiple models. However, three clinical studies exploring the role of single dose or multiple doses of ABT-639 (100 mg) in diabetic neuropathy have not found significant pain-attenuating actions. The present review discusses the unsuccessful clinical trials of peripherally acting ABT-639 in patients with diabetic neuropathy.